Comment by dredmorbius

10 hours ago

All matter (stuff interacting with gravity) is attracted toward other gravitational centres, however all matter also has momentum, which may tend to carry it away from that centre. Objects don't merely fall directly toward a gravitational centre, but, subject to their initial velocity, orbit it. You may find yourself thankful for this on reflection, as the body you're likely resting on has been in such an orbit for roughly 4.5 billions of years, and will continue to be so for roughly a similar period of time.

If you're sufficiently close to the mass, and/or its radius (relative to your own and your distance from it) is large, as with, say, a stone tossed from ground level on Earth, that orbit will intersect the surface rather quickly.

At astronomical distances, ranging from some significant fraction of the distance between the Earth and Moon to interstellar and intergallactic distances, it's far more likely that an attraction will result in some other form, generally an ellipse (typical of a captured orbit), circle (a perfectly non-eccentric ellipse), a parabola (object moving at escape velocity), or hyperbola (object moving faster than escape velocity).

Ring systems form as multiple masses interact around a larger mass, be that a moon, planet, star / quasi-stellar object, galaxy, or other mass. Until the tangential velocity is lost, the particles within the ring will continue their orbit. Occasional interactions and collisions, as well as radiated energy (including gravitational radiation) may cause a given particle to spiral inwards, or be ejected from, the ring system.